This year is the 70th anniversary of the establishment of the Manhattan Project, a predecessor of the U.S. Department of Energy. In honor of its impacts on science and history, a 'Manhattan Project' series on this blog will revisit various aspects of its background, establishment, operations, and immediate and long-term influences. The first of the series is about the background of the Manhattan Project.

During the fall of 1939, President F. D. Roosevelt was made aware of the possibility that German scientists were racing to build an atomic bomb and he was warned that Hitler would be more than willing to resort to such a weapon. As a result, Roosevelt set up the Advisory Committee on Uranium, consisting of both civilian and military representatives, to study the current state of research on uranium and to recommend an appropriate role for the federal government. The result was limited military funding for isotope separation and the work on chain reactions by Enrico Fermi and Leo Szilard at Columbia University.

On a separate front, in late 1939 Vannevar Bush, president of the Carnegie Foundation, became convinced of the need for the government to marshal the forces of science for a war that would inevitably involve the United States. In June 1940, Roosevelt established a voice for the scientific community by establishing the National Defense Research Committee (NDRC), a reorganization of the Advisory Committee on Uranium into a scientific body that eliminated military membership. The NDRC would have more influence and more direct access to money for nuclear research. The NDRC's early priorities were studies on radar, proximity fuzes, and anti-submarine warfare with continued isotope separation and chain reaction work.

During 1939 and 1940, most of the research on isotope separation and chain reaction work was performed in university laboratories by academic scientists. Ernest O. Lawrence, director of the Radiation Laboratory at the University of California at Berkeley, wanted the government to mobilize its scientific forces as rapidly as possible. Specifically on his mind were experiments taking place in his laboratory. These included studies on uranium fission fragments by Edwin M. McMillan and Philip H. Abelson and research by Glenn T. Seaborg.

In 1941, Vannevar Bush became director of the Office of Scientific Research and Development (OSRD), which was established by Executive Order on June 28, 1941, and strengthened the scientific presence in federal government. At this time, the NDRC became an advisory body to OSRD and the Uranium Committee became the OSRD Section On Uranium with the code name S-1. Under the auspices of OSRD, S-1 was strengthened by the addition of Fermi as head of theoretical studies and Harold C. Urey as head of isotope separation and heavy water research.

In March 1942, with approval by Roosevelt, the Army Corps of Engineers began to participate in S-1 meetings. This reflected the need for security within the S-1 program coupled with the Corps' expertise in construction, which would be needed to build the production facilities required for making the atomic bomb. An Army officer would be in overall command of the entire project. With this reorganization in place, the nature of the American atomic bomb effort changed from one dominated by research scientists to one in which scientists played a supporting role in the construction enterprise run by the U.S. Army Corps of Engineers.